This application claims the priority of the Swiss patent application No. 830/00 filed on Apr. 27, 2000, the disclosure of which is incorporated herein by reference in its entirely.
The present invention relates to static mixing elements and to single stage static mixing element segments having a tubular mixing channel with mixing vanes arranged in that channel. Furthermore the present invention relates to static mixers with static mixing elements and/or single stage static mixing element segments of the before mentioned type, to a mixing vanes element for arrangement in a tubular mixing channel and to a method for mixing very viscous goods, in particular very viscous polyurethane with a curing accelerating agent.
Generally, static mixing elements resp. static mixers are used in applications where two or more streams of free-flowing goods have to be mixed to one substantially homogeneous stream. In the field of adhesives, there are known disposable static mixers for two component adhesive systems which consist of a plastics tube forming a mixing channel and, arranged in lose manner inside that tube, a one-piece mixing unit made of plastics whose mixing vanes are designed as swirl vanes. In the center, said mixing vanes are interconnected with each other in such way that they form a coherent mixing vanes element. Inside said tube, said mixing vanes element abuts, in the area of the exit of said tube, with its mixing vanes which are arranged in flow direction axial at the last position on an axial shoulder of the tube and thereby is, axially in flow direction, supported.
While this mixer design yields good results when mixing low viscous goods at low to medium flow rates, the results when mixing very viscous materials resp. at high flow rates are not satisfactory.
Hence, it is a general object of the invention to provide static mixing elements, single stage static mixing element segments, static mixers, a mixing vanes element and a method for mixing very viscous goods, in particular very viscous polyurethane with a curing accelerating agent, which do not have the before mentioned disadvantages and can be manufactured or performed at low costs.
A first aspect of the invention concerns a static mixing element for mixing at least two components, comprising
a mixing channel of substantially tubular shape which is undivided in axial direction and is formed by at least two separate radial segments and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
mixing vanes arranged in said mixing channel which radially abut on said inner wall of said mixing channel and which are formed by at least one element which is separate from said mixing channel, wherein said mixing vanes comprise a last mixing vane which is arranged axially in flow direction at a last position of said mixing vanes and at least one second mixing vane which is arranged axially in flow direction before said last mixing vane, and wherein at least one of said at least one second mixing vane is, in an area where it radially abuts on said inner wall of said mixing channel, interconnected with said inner wall for transferring axial forces to said mixing channel.
Thus, mixing channel and mixing vanes are formed by separate elements and one or more mixing vanes which are arranged on a position not being, in flow direction, the last axial vane position are interconnected with said inner wall for transferring forces which act in axial direction from said vanes to the inner wall of said mixing channel. This interconnection, which can be established by positive locking, by frictional connection, by glueing or welding or by a combination thereof, effects a stabilization of the axial position of the mixing vanes in the entry area of the mixing element.
As has been mentioned earlier, the inner wall of the mixing channels forms the outer boundary of the cross section of the mixing channel through which the components flow when they pass through the mixing element for being mixed. It encloses this flow path and is, with a large area, in contact with this stream of components. The inner contour of the mixing channel is tubular and preferably of substantially round, preferably of circular cross section. Substantially round cross section means a cross sections with a shape which prevents the formation of dead corners, like e.g. oval cross sections or cross sections of a polygonal shape that approximate a round, oval or similar cross section.
In case a non-round cross section is chosen, a mixing element can be provided in which, when using a uniform swirl vane distribution, the flow is alternately accelerated and decelerated. This can be of advantage in certain applications. Beside the before mentioned shapes of the cross section of the mixing channel it is also planned to use mixing channels with substantially angular and preferably square cross sections. Especially in case the mixing vanes in the mixing channel are simple turbulence vanes oriented transversely to the flow direction of the mixing element, such a cross section can be advantageous.
A mixing channel which in undivided in axial direction is a mixing channel whose inner wall is formed at a given radial position over its entire axial extension by a one-piece element. This means in other words that this mixing channel might be formed by several radial segments each extending over its entire length, but, however, not by several axial segments.
Preferably, the mixing channel is formed by exactly two radial segments each forming one half of said channel.
A second aspect of the invention concerns a static mixing element for mixing at least two components comprising
a mixing channel of substantially tubular shape and of a, in axial direction, substantially constant cross section which is formed by a one-piece element and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
mixing vanes arranged in said mixing channel which radially abut on said inner wall of said mixing channel and which are formed by at least one element which is separate from said mixing channel, wherein said mixing vanes comprise a last mixing vane which is arranged axially in flow direction at a last position of said mixing vanes and at least one second mixing vane which is arranged axially in flow direction before said last mixing vane, and wherein at least one of said at least one second mixing vane is, in an area where it radially abuts on said inner wall of said mixing channel, interconnected by positive locking and/or frictional connection with said inner wall for transferring axial forces to said mixing channel.
A third aspect of the invention concerns a static mixing element for mixing at least two components comprising
a mixing channel of substantially tubular shape which is formed by a one-piece element and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
mixing vanes arranged in said mixing channel which radially abut on said inner wall of said mixing channel and which are formed by at least one element which is separate from said mixing channel, wherein said mixing vanes comprise a last mixing vane which is arranged axially in flow direction at a last position of said mixing vanes and at least one second mixing vane which is arranged axially in flow direction before said last mixing vane, and wherein at least one of said at least one second mixing vane is, in an area where it radially abuts on said inner wall of said mixing channel, interconnected by positive locking through penetration of protrusions in recesses with said inner wall for transferring axial forces to said mixing channel.
In a preferred embodiment of one of the preceding three aspects, the mixing vane or the mixing vanes which are arranged in flow direction axial at the first position, or, in other words which are located at the entry of the mixing channel as such, are interconnected with the inner wall of the mixing channel. Surprisingly it has been found that stabilising the axial position of the mixing vanes in the area where the vanes abut on the inner wall, and especially in the entrance of the flow channel formed by the mixing vanes, leads to a substantial improvement of the mixing results when mixing very viscous goods, e.g. pasty materials, or goods at high flow rates. Since it appears that the correct axial position of the mixing vanes, especially in the entry area, is of utmost importance for the mixing result, the advantages of the invention best become apparent at extremely long mixing elements which have a multitude of mixing vanes arranged in axial direction one after another. At such mixing elements, the possible wrong positioning in axial direction of the mixing vanes which are arranged in flow direction at the first position due to a deformation of the mixing vanes element caused by forces applied to the vanes by the flow of goods passing through the mixing element is relative huge.
In a further preferred embodiment of one of the preceding three aspects, at least two mixing vanes which are in axial direction arranged one after another are, in an area in which they radially abut on the inner wall of the mixing channel, interconnected with said inner wall. Since these mixings vanes are directly supported in axial direction by the mixing channel, a stable mixer geometry, even in cases where relative big forces are applied to the mixing vanes, is achieved. Furthermore it is of advantage for the stability if, in addition, the mixing vanes which are arranged in axial direction one after another and/or which are arranged at the same axial position are interconnected with each other. Especially in case they are interconnected in an area near the center of the mixing channel, in combination with the interconnection of the mixing vanes with the inner wall of the mixing channel, dimensionally extremely stable mixing elements result.
Preferably, at least two mixing vanes form a coherent mixing vanes element. This is, by advantage, achieved by a common one-piece design of the mixing vanes. In this case, a mixing element results which has a simple construction and is composed of only a few components that can be manufactured in a cost effective manner. However, it is also planned to stick together or to glue or weld together individual mixing vanes to a mixing vanes element. A mixing vanes element can e.g. consist of at least two mixing vanes which are arranged at the same axial position, however it is preferred if it comprises at least two mixing vanes which are in axial direction arranged one after another and are, for example, interconnected with each other in the center of said element.
Also preferred are embodiments of one of the preceding three aspects at which mixing vanes of the mixing vanes element, which are arranged in axial direction one after another, are interconnected with each other, in an area which abuts on the inner wall of the mixing channel, through supporting pillars. This interconnection can e.g. be effected by a one-piece design in which the interconnected mixing vanes and the pillars are formed by a single element. However, there are also embodiments planned having individual pillars affixed between the mixing vanes or having mixing vanes comprising pillar-like portions that axially abut on each other for supporting each other.
A further preferred embodiment of the mixing element of one of the preceding three aspects comprises at least two such mixing vanes elements, which are preferably arranged axially one after another in the mixing channel. However, it is also foreseen to arrange individual mixing vanes elements beside each other in the mixing channel or to use a combination of both arrangements.
In the described way, it is possible to compose, from only a few standardised mixing vanes elements, static mixing elements of various length resp. with different numbers of mixing stages and to overcome problems in the manufacturing of mixing vanes elements.
In a preferred embodiment of one of the preceding three aspects, the mixing vane or the mixing vanes which are interconnected with the inner wall of the mixing channel resp. the mixing vanes element or the mixing vanes elements is or are interconnected with the mixing channel in axial direction through positive locking. By advantage, this is achieved through a penetration of protrusions formed by the mixing vanes or the mixing vanes element and/or the inner wall of the mixing channels into recesses formed by said mixing vanes or said mixing vanes element and/or said inner wall. Preferably, the mixing vanes which are interconnected with the inner wall radially protrude into one or several recesses in the inner wall of the mixing channel, thereby creating a positive locking situation axially in flow direction between said mixing vanes and said inner wall of said mixing channel. Furthermore, it is preferred if said recesses have substantially the shape of said mixing vanes in said area where said mixing vanes protrude into said recesses.
Furthermore, the positive locking situation between the mixing vanes resp. the mixing vanes element and the inner wall of the mixing channel can be achieved by adapting the outer contour of the mixing vanes or of the mixing vanes element and the contour of the inner wall of the mixing channel in such way that they together form a bayonet connection or a threaded connection, that protrusions snap-in into recesses or that additional elements like e.g. radial pins can effect a positive locking. In case mixing vanes elements are used whose mixing vanes are, in an outer area of said mixing vanes element, interconnected with each other by supporting pillars, it is foreseen that said pillars are arranged in recesses in the inner wall of the mixing channel. This is, in particular, reasonable in case these supporting pillars comprise means for causing an axial positive locking situation with said mixing channel.
In yet another preferred embodiment of one of the preceding three aspects, the mixing vane or the mixing vanes which are interconnected with the inner wall of the mixing channel resp. the mixing vanes element or the mixing vanes elements is or are in axial direction frictionally connected with the mixing channel, e.g through clamping. Also combinations of positive locking and frictional connection are planned, like e.g. mixing vanes elements having resilient vanes made of sheet steel. These elements can, under resilient slanting of said mixing vanes, be inserted, against flow direction, into a mixing channel e.g. made of plastics, and straddle against the inner wall of the mixing channel, after being properly positioned, upon being loaded through the forces applied to the vanes by the flow of goods through the mixing channel. With increasing axial forces in flow direction, the straddling forces increase as well, causing the sharp-edged steel vanes to interlock in said relative soft inner wall of said mixing channel.
Preferably, the mixing vanes are designed as swirl vanes, i.e. they are designed in such way that goods which have to be mixed are, in the area that is influenced by them, caused to turn around an axis of the mixing channel. In particular, it is preferred that swirl vanes which are arranged axially one after another have opposite swirl directions.
It is understood that other, not explicitly mentioned combinations like e.g. the use of supporting pillars in the area where the mixing vanes element abuts on the inner wall of the mixing channel together with a glue or welding connection of the same with the inner wall and/or together with a positive locking connection in axial direction with the mixing channel also are possible.
A fourth aspect of the invention concerns a static mixing element for mixing at least two components comprising
a mixing channel of substantially tubular shape which is undivided in axial direction and is formed by at least two separate radial segments and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
mixing vanes arranged in said mixing channel which radially abut on said inner wall of said mixing channel and which are one-piece with at least one of said radial segments and wherein at least two of said mixing vanes are axially arranged one after another and wherein said mixing vanes of at least one of said radial segments preside over a split plane which is defined by radial split seams formed by said radial segment.
By such a design, it is for example possible to obtain an overlap of the radial extensions of the mixing vanes of two mixing channel segments which each form one half of the mixing channel.
The cross section of the mixing channel can have the same shapes as the one of the static mixing elements according to the preceding aspects.
In a preferred embodiment, the mixing channel is formed by two radial segments which each form one half of said mixing channel and which preferably comprise at least two mixing vanes each.
In another preferred embodiment, the mixing vanes which are in axial direction arranged one after another and/or which are arranged at the same axial position are interconnected with each others for transferring forces to each other which act in axial direction. This interconnection preferably is established in a central area of the mixing channel. In case it is desired to interconnect the mixing vanes of an individual radial segment of the mixing channel which are arranged axially one after another, it is preferred to interconnect these vanes in the area of the center of the mixing channel through a one-piece design, e.g. by forming them as one piece together with a central pillar. In case it is desired to interconnect the mixing vanes of at least two radial segments of the mixing channel with each other, it preferred to interconnect them in the area of the center of the mixing channel by generating a positive locking situation, e.g. in the fashion of intersecting teeth of two combs which are formed by the tips of the mixing vanes of said radial segments.
In yet another preferred embodiment of this static mixing element, the mixing vanes are designed as swirl vanes wherein it is preferred that swirl vanes which are arranged axially one after another have opposite swirl directions. Furthermore it is preferred to manufacture said static mixing element from plastics, preferably by injection moulding.
In a preferred embodiment of one of the static mixing elements according to one of the first four aspects of the invention, the extensions in a direction transverse to a axis of said mixing channel of the mixing vanes which are axially arranged one after another overlap around said axis by an angle of between 30xc2x0 to 90xc2x0.
A fifth aspect of the invention concerns a single stage static mixing element segment for mixing at least two components comprising
a mixing channel of substantially tubular shape which is formed by at least two separate radial segments and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
at least one mixing vane arranged in said mixing channel.
Single stage means that this mixing element segment does not have mixing vanes which are arranged axially one after another. In case such a mixing element segment comprises several mixing vanes, these mixing vanes are arranged substantially on the same axial position.
In a preferred embodiment of the single stage mixing element segment, the mixing channel is formed by two radial segments each forming one half of said mixing channel.
Preferably, the single mixing vane is or the several mixing vanes are interconnected with the inner wall of the mixing channel by positive locking, by frictional connection (e.g. through clamping), by glueing or welding or by a combination thereof. It is, however, also planned to interconnect said mixing vanes with said inner wall by forming a vane and a part of the inner wall as a one-piece element.
A sixth aspect of the invention concerns a single stage static mixing element segment for mixing at least two components comprising
a mixing channel of substantially tubular shape which is formed by a one-piece element and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
at least one mixing vane arranged in said mixing channel which is formed by at least one element which is separate from said mixing channel and which is interconnected with said inner wall of said mixing channel by positive locking and/or by frictional connection.
In a preferred embodiment of the fifth or the sixth aspect of the invention, the single stage static mixing element segment comprises at least two mixing vanes which are, preferably in the area of the center of the mixing channel, interconnected with each other for transferring axial forces to each other. Furthermore, it is preferred that the single stage mixing element segment of one of the two before mentioned aspects comprises exactly two mixing vanes which are symmetrically arranged around a central axis of the mixing channel.
The cross section of the before described single stage mixing element segments according to the fifth or the sixth aspect of the invention can have all shapes that have already been discussed for the static mixing element according to the first four aspects of the invention. The same applies for the possible extensions of the mixing vanes in the mixing channel. Furthermore, it is preferred that the mixing vanes are designed as swirl vanes.
Generally, for all the before mentioned aspects concerning static mixing elements or single stage static mixing element segments, it is planned to manufacture the mixing vanes and/or the part or the parts forming the mixing channel from plastics, preferably by injection moulding.
A seventh aspect of the invention concerns a static mixer comprising at least one static mixing element and/or at least one single stage static mixing element segment according to one of the preceding aspects of the invention.
Preferably, the static mixer comprises a housing for receiving said at least one static mixing element and/or said at least one single stage static mixing element segment.
In a preferred embodiment, the static mixer for mixing at least two components comprises
a static mixing element having
a mixing channel of substantially tubular shape which is undivided in axial direction and is formed by at least two separate radial segments and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
mixing vanes arranged in said mixing channel which radially abut on said inner wall of said mixing channel and which are formed by at least one element which is separate from said mixing channel, wherein said mixing vanes comprise a last mixing vane which is arranged axially in flow direction at a last position of said mixing vanes and at least one second mixing vane which is arranged axially in flow direction before said last mixing vane, and wherein at least one of said at least one second mixing vane is, in an area where it radially abuts on said inner wall of said mixing channel, interconnected with said inner wall for transferring axial forces to said mixing channel and
a housing in which said static mixing element is arranged.
In another preferred embodiment, the static mixer for mixing at least two components comprises
a static mixing element having
a mixing channel of substantially tubular shape which is undivided in axial direction and is formed by at least two separate radial segments and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
mixing vanes arranged in said mixing channel which radially abut on said inner wall of said mixing channel and which are one-piece with at least one of said radial segments and wherein at least two of said mixing vanes are axially arranged one after another and wherein said mixing vanes of at least one of said radial segments preside over a split plane which is defined by radial split seams formed by said radial segment and
a housing in which said static mixing element is arranged.
Preferably, the static mixer according to the seventh aspect further comprises an application nozzle.
An eighths aspect of the invention concerns a mixing vanes element for mixing at least two components, for arrangement in a mixing channel of substantially tubular shape which forms with an inner wall in radial direction an outer boundary of a cross section for receiving said components, comprising at least two mixing vanes which are in axial direction arranged one after another and wherein said mixing vanes which are arranged in axial direction one after another are, in an outer area, interconnected with each other through supporting pillars for transferring axial forces to each other.
In a preferred embodiment, said pillars are formed as one piece with said vanes which they interconnect. However, there are also embodiments planned at which individual pillars are affixed between said mixing vanes e.g. by glueing, welding or by stick-in connection, or at which the mixing vanes abut on and support each other through pillars formed by each of the individual mixing vanes.
In another preferred embodiment of the mixing vanes element, the mixing vanes which are arranged in axial direction one after another and/or which are arranged at the same axial position are interconnected with each other in the area of the center of said mixing vanes element for transferring axial forces to each other. By advantage, they are connected in such way that they form one piece in this area. By the before mentioned design, a mixing vanes element with a, in axial direction, quite sturdy structure is achieved which prevents, even at high flow forces like they are experienced when mixing very viscous goods or applying high flow rates, a deformation and a change in position of the mixing vanes. Both would affect the mixing quality. Even when using this mixing vanes element together with a conventional mixing channel, which merely provides a shoulder for axial abutment and support of the mixing vanes element at its outlet, good mixing results are achieved under the before mentioned conditions.
In a further preferred embodiment, the supporting pillars comprise means for effecting a positive locking situation with the inner wall of a mixing channel which receives the mixing vanes element. In combination with a suitable mixing channel this leads to an extremely stable arrangement.
Like with the before described static mixing elements, it is also preferred that the mixing vanes of this mixing vanes element are designed as swirl vanes, preferably with a different swirl direction of vanes which are arranged in axial direction one after another, and that the element is made of plastics, preferably manufactured through injection moulding.
A ninth aspect of the invention concerns a method for mixing very viscous components with the static mixing element, the single stage static mixing element segment, the static mixer or the mixing vanes element according to one of the preceding aspects of the invention.
In a preferred embodiment, the method for mixing very viscous polyurethane and a curing accelerating agent comprising the steps of
providing a static mixing element having
a mixing channel of substantially tubular shape which is undivided in axial direction and is formed by at least two separate radial segments and wherein an inner wall of said mixing channel in radial direction forms an outer boundary of a cross section for receiving said components and
mixing vanes arranged in said mixing channel which radially abut on said inner wall of said mixing channel and which are formed by at least one element which is separate from said mixing channel, wherein said mixing vanes comprise a last mixing vane which is arranged axially in flow direction at a last position of said mixing vanes and at least one second mixing vane which is arranged axially in flow direction before said last mixing vane, and wherein at least one of said at least one second mixing vane is, in an area where it radially abuts on said inner wall of said mixing channel, interconnected with said inner wall for transferring axial forces from said second mixing vane to said mixing channel and
effecting said polyurethane and said curing accelerating agent to simultaneously flow through said mixing channel of said static mixing element for mixing them.